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      Phase separation in liquid crystalline mesophases of [Co(H 2O)6]X2: P65 Systems (X = NO3-, Cl-, or ClO4-)

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      Author
      Albayrak, C.
      Gülten, G.
      Dag, Ö.
      Date
      2007
      Source Title
      Langmuir
      Print ISSN
      0743-7463
      Volume
      23
      Issue
      2
      Pages
      855 - 860
      Language
      English
      Type
      Article
      Item Usage Stats
      109
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      Abstract
      Transition-metal aqua complex salts [M(H2O)6]X 2 (where M is Mn(II), Co(II), Ni(II), Zn(II), or Cd(II) and X is NO3-, Cl-, or ClO4-) can be dissolved in triblock poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) copolymers (Pluronics, such as P65) to form homogeneous liquid crystalline (LC) mesophases. However, the [Co-(H2O) 6]X2:P65 LC mesophases slowly undergo phase separation into a disordered ion-free phase and an ordered ion-rich LC mesophase. The phase separation also takes place in the two-salt systems [Co(H2O) 6](NO3):[Co(H2O)6]-(ClO 4)2:P65 in which the ion-free disordered domains separate out from the initially ordered homogeneous mesophase. The phase separation results in a physical mixture of a hexagonal nitrate-rich and cubic perchlorate-rich LC and disordered ion-free domains in the mixed salt systems. The driving force in the phase separation in the [Co(H2O) 6]-X2:P65 system is Co(II)-catalyzed aerobic oxidation of P65 into ester and/or other oxidation products. The separation of ions in the [Co(H2O)6](NO3)2:[Co(H 2O)6](ClO4)2:P65 system is related to the mesostructures of the two-salt systems that are different, hexagonal in the [Co(H2O)6](NO3)2:P65 system and cubic in the [Co(H2O)6](ClO4)2:P65 system. There is no visible phase separation in the other transition-metal salt:P65 systems. The phase separation in the [Co-(H2O) 6]X2:P65 systems can also be eliminated by keeping the mesophase under a N2 atmosphere. © 2007 American Chemical Society.
      Keywords
      Block copolymers
      Complexation
      Dissolution
      Liquid crystals
      Oxidation
      Phase separation
      Salts
      Aerobic oxidation
      Ion free phase
      Liquid crystalline mesophases
      Mixed salt systems
      Transition metal compounds
      Permalink
      http://hdl.handle.net/11693/23559
      Published Version (Please cite this version)
      http://dx.doi.org/10.1021/la0622119
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